Glutamic acid, also known as α-aminoglutaric acid or 2-amino pentanedioc acid, is a nonessential amino acid with the chemical formula COOH(CH2)2CH(NH2)COOH (FW=147.13 g, CAS No. 56-86-0). The naturally occurring form is the L(+)-glutamic acid (mp=205° C. with decomposition). It is usually found in foodstuffs and drinks as the sodium salt, monosodium glutamate, also known as sodium glutamate or MSG, with the chemical formula COOH(CH2)2CH(NH2)COONa (FW=187.14 g, CAS No. 6106-04-3). MSG (mp=232° C. with decomposition). MSG is used as a flavor enhancer in foodstuffs and drinks at about 0.3%.
Many people have an allergic or adverse reaction to MSG in food. Symptoms vary in type and magnitude but can include rashes and swelling of the throat. Tolerance levels vary person to person but sensitive people can react to 5 g of MSG, whereas non-sensitive people can tolerate up to 25 g. MSG is found in more than Chinese cooking. It occurs naturally in parmesan cheese, tomatoes, spinach, mushrooms, and seaweed. It is also in tuna and some ice creams. The issue is that it is also hidden in foods as a flavor enhancer. If you are Type II diabetic, then the MSG can raise your blood pressure. MSG is especially bad for anyone with Renal Failure (kidney failure).
MSG is known as monosodium glutamate, glutamate, glutamic acid, Accent®, Ajinomoto®, hydrolyzed oat flour, Glutavene®, and L-cysteine. MSG is almost always present in glutamate, yeast extract, hydrolyzed protein, glutamic acid, calcium caseinate, sodium caseinate, yeast food, gelatin, textured protein, yeast nutrient, and autolyzed yeast. MSG is often found in natural beef flavorings, stock, broth, malt extract, soy sauce, and soy protein. So although a chef might not deliberately add MSG to his cuisine, it may be added accidentally in a broth or other ingredient.
Since it is very difficult to determine what foodstuffs might actually contain MSG, there is a strong need for a field test kit that can determine the presence of MSG in foodstuffs and drinks quickly and efficiently in a non-laboratory environment such as a restaurant or other dining establishment.
A survey of the literature indicated very few chemical systems that would be appropriate to use in the present invention. It was decided that a colorimetric change would be required for an inexperienced person to determine a positive reaction to MSG. A spot reaction test was found that was reported to be effective at very low levels of an alpha-amino acid.1 
This spot test method involves the detection of an α-amino acid through condensation with pyridine-2-aldehyde to form a Schiff base (an imine). Pyridine is used to ensure the availability of the amino group for reaction by neutralization of the carboxylic acid group. Cobalt nitrate is used as a chelating agent to give a colored species that can be visually determined. This method requires mixing a reagent and then heating the reagent with the sample for one to three minutes.
There is no reported data regarding the reaction with MSG. However, the method is very sensitive to α-amino acids. The following materials tested positive: 3 γ cystine, 3 γ cysetine, 2.5 γ methionine, 5 γα-alanine, 2 γ lysine, 1 γ glycine, 3 γ tyrosine, 1 γ L-leucine, 5 γ aspartic acid, and 5 γ asparagine. A positive response was also obtained for monoiodo-L-tyrosine, valine, citrulline, arginine, phenylalanine, tryptophan, and 2-amino-n-octanoic acid.
The issue with the reagents selected for the colorimetric reaction is the short shelf-life once the reagent is prepared by mixing the pyridine-2-aldehyde solution and the cobalt nitrate solution. It is reported that the shelf life is only one week which would make this system unacceptable for a field test kit.
In U.S. Pat. No. 5,824,554 a dining mat, such as a doily, composed of absorbent material and small spots of applied reagents was used to determine the presence of allergenic substances.2 In use, food is applied to the reagents on the dining mat, and the reagent changes its appearance indicating the presence of the allergenic substance in the food product. The advantage of this method is that only a small sample of food is required and the food is not contaminated by the testing. However, although MSG was listed as an allergenic material, there was no mention of any reagent system that might allow for the detection of MSG in the food. Since the spot test requires the use of a liquid reagent, namely pyridine-2-aldehyde, this dining mat method using the reagents of the spot test method will not work for MSG. At best, the dining mat method will suffer the same short shelf-life issue as the mixture of reagents from the spot test.
Therefore, a solution to this shelf-life issue is provided by this invention while maintaining the advantages of convenience of use and no food contamination found in the prior art. An encapsulating material is needed to keep the reactive chemicals separate until they are required to react with the foodstuff. Since the colorimetric reaction occurs at near boiling water temperature, it is desirable to have this encapsulating material melt below that temperature. It has been surprisingly found that a low melting paraffin wax can function as an encapsulating material.